Triumph Speed Four
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Introduced in 2002, the Triumph Speed Four is the naked (non-faired) brother of the TT600 sportbike introduced in 1999. While the TT600 was prone to fuel injection problems, these were fixed for the 2002 Speed Four. While aesthetically similar to the larger Speed Triple, the Speed Four has an entirely different frame and engine. Power comes from a 599 cc inline-four cylinder engine, the same engine in the TT600 but tuned for better midrange, it produces 98 hp @11750 rpm, with a 13,500 rpm redline, and a respectable 50.2 ft·lbf (68.1 N·m) of torque at 9750 rpm. With a dry weight of only 375 lb (170kg), the Speed Four is a phenomenal street machine that is also capable of handling track duty. The bike has a top speed of 135mph and a 0-60 time of about 3.5 seconds.
The Speed Four in fact is mechanically very nearly identical to its predecessor, the TT600, with the exceptions of the cam profiles, ignition and fuel injection mapping, front spring rate, and other minor concessions to its streeetfighter style; the frame and fully adjustable suspension are race-ready. With the addition of a race exahust and ignition mapping, the bike's performance is comparable to any 600cc four of the period. The Speed Four's only aesthetic relationship to the Speed Triple is the bug-eyed headlight pair and bikini fairing; the Speed Four even retains the clip-ons of the TT600, versus the motocross inspired handlebars of the Speed Triple and other streetfighters like the Tuono, FZ-1, Monster, etc.
The handling of the bike is generally superb and eminently adjustable. The engine makes broad, smooth power from 5000 rpm all the way to redline at 13,500 rpm, with serious boost and growl kicking in at 8000 rpm. Above 8000 rpm the Speed Four, like many 600s of its class, makes power that is very difficult to apply on the street; 10,000 rpm in third gear will see the operator exceeding any speed limit in the United States. This is, therefore, a highly capable, high-performance machine, very capable for track use. At street speeds the Speed Four cruises effortlessly between 5,000-8,000 rpm. The gearbox is geared tall, but there are no gaps between gears due to the engine's strong, broad output. Wind protection is surprisingly quite good; although the bikini fairing appears small, it is nonetheless adequate, and the girth of the inline four itself provides ample protection for the legs, despite the absence of a lower fairing.
Speed Fours are notorious for a poorly designed crankcase breather seal, which causes small amounts of oil to blow back into the airbox. Eventually the oil drips from the airbox onto the lower end and from there to the ground. While the amount of oil lost is negligible and does not affect performance, the drip is unsightly and leads to many comments about Triumphs leaking oil—an infamous trait of the vertically-split cases of 1960s vintage Triumph parallel twins, such as the original Bonneville. Such a drip is also unacceptable for bikes to be used on the racetrack, and there is a chance that oil might contaminate the rear tyre leading to loss of traction.
The Speed Four was voted No.1 for handling and suspension in Ride magazines Rider Power Surevy, Triumphs Daytona 675 was 2nd in the same category.
A popular Speed Four website and forum can be found at Speedfour.org
Competition for the Speed Four includes Suzuki's SV650 and Bandit 600/650, Honda's CBF600 hornet, Yamaha's FZS600 Fazer, Kawasaki's z750, and ER6 and Ducati's Monster.
